The implantation of occlusive systems for fully or partially occluding a natural conduit of a patient is known for different indications.
For example, the treatment of urinary incontinence can involve implantation of an artificial sphincter in a patient.
Such a sphincter typically comprises an occlusive element placed around the urethra (in men or women) or sometimes the bladder neck (in women) or the prostate (in men) with the aim of exerting direct or indirect compression on the urethra to prevent urinary leaks, an activation device of said occlusive element to vary compression exerted on the urethra or the bladder neck, as well as a control unit of the activation device.
In the case of a hydraulic system, the occlusive element is an inflatable cuff containing a variable volume of fluid and the activation device comprises a reservoir containing fluid in fluidic connection with the cuff and an actuator for adding or removing said fluid to compress or decompress the cuff.
Such an artificial sphincter is described in particular in [1] and [2].
Another example of artificial sphincter is described in [3].
In such a system, it is possible that slow leaks occur in the hydraulic circuit.
«Slow leak» means in the present text a loss (respectively an addition) of liquid in a small quantity and stretching over a long period (at least several days, but more generally of the order of several months), causing a progressive drop (respectively a rise) in the pressure in the hydraulic circuit.
By opposition, a leak is considered as rapid if it causes a sharp decrease of pressure in the hydraulic circuit.
In this way, a rapid leak is detectable as soon as the triggering event has taken place (for example, disconnection of the tubing connecting the cuff to the fluid reservoir) or shortly after (for example, substantial damage of one of the materials ensuring sealing).
On the contrary, a slow leak becomes detectable only several days, or even several months after the occurrence of the breakdown which is the cause.
Such slow leaks can have different causes, including:                damage to a mechanical element of the hydraulic circuit, for example cracking of an element,        a defect of the connection of the tubing to the reservoir or to the occlusive cuff,        the porosity of the material constituting the tubing and/or the occlusive cuff (generally made of silicone) and inadequate concentration of the saline solution contained in the hydraulic circuit, generating a concentration gradient between the extracellular medium and the hydraulic circuit, which causes diffusion of water from the least concentrated medium to the most concentrated medium. In particular, if the fluid contained in the hydraulic circuit is insufficiently concentrated (hypotonic) relative to the external medium, the water will tend to diffuse to the exterior of the hydraulic circuit, leading to a decrease in the volume in said circuit; by contrast, if the fluid contained in the hydraulic circuit is too concentrated (hypertonic), there will be diffusion of water coming from the exterior to the hydraulic circuit, resulting in a rise in volume [4].        
The effect of a slow leak is to alter the operation of the occlusive system.
In fact, for the same activation instruction, the fact that the hydraulic circuit contains less fluid or more than during implanting of the occlusive system results in a variation of the compression exerted on the conduit to be occluded.
In the case of where the slow leak leads to a loss of fluid, it can involve a decrease in the occlusion exerted by the cuff, and consequently a decrease in the efficacy of the occlusive system.
In the case of where the slow leak leads to an addition of fluid, it involves a progressive rise in pressure in the hydraulic circuit, causing excessive compression of the tissues surrounded by the cuff.
Occlusive systems proposed currently fail to detect a slow leak in the hydraulic circuit and to alert the patient or the practitioner thereof.
An aim of the invention is therefore to design a method and device for detecting this type of leak and, if needed, alert the practitioner or the patient.